//NaN 实例
var month = 0
if (month <= 0 || month > 12) {
    month = Number.NaN
    console.log("月份是：" + month)
} else {
    console.log("输入月份数值正确。")
}
//prototype 实例
function employe1(id: number, name: string) {
    this.id = id
    this.name = name
}
var emp = new employe1(123, "admin")
employe1.prototype.email = "admin@runoob.com"

console.log("员工号: " + emp.id)
console.log("员工姓名: " + emp.name)
console.log("员工邮箱: " + emp.email)